YouTube Service for Keyring

In 7072886 I added a first swing at a YouTube Service definition to Keyring. It’s based heavily on the Google Analytics one that was recently submitted via PR. It’s not part of an official release yet. I’m curious about enabling people to import the videos they publish on YouTube into a WordPress install though, as that feels like something that folks who use it heavily would want as part of their web presence.

Next step will be adding an importer for YouTube, which I'll probably aim to do over the coming weeks.